Sound reproducer



May 5, 1925. 1,536,118 B. s. MCCUTCHEN SOUND REPRODUCER Filed April 1, 24

jwgmze 10 INVENTOR 17. Jflfchtckel/y BY ATTO RNEY Patented May 5, 1 925.

l UNITED STATES PATENT OFFICE.

BBUNSON B. IOC UTCHEN', OI FORTH YLAINIIELD, NEW JERSEY, ASSIGNOR TO AMERI- CAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

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Application ma April 1, 1024. Serial no. 703,504).

To all whom it may concern:

Be it known that I, Bronson S. Mc- CU'rcnEN, residing at North Plainfield, in the county of Somerset and State of New Jersey, have invented certain Improvements in Sound Reproducers, of which the followin is a specification.

his invention relates to sound reproducers and more particularly to sound reproducers of the type known as loud speakers.

An object of the invention is to provide a loud speakerwhich will efiectively transmit a wide range of f uencies without undue distortion. This 0 ject and other objects of the invention are attained by providing a doubly resonant arrangement comprising two diaphragms of different dimensions and difi'erent degrees of stiffness. One of these diaphra ms may have a natural period corres in to a low telephonic frequency an the ot er may have a natural period corresponding to a high telephonic fr uency. The two diaphragms are mechanical y connected to be operated by a suitable magnetic arrangement.

[Further details of the invention will be clear from the following description when read in connection with the accompanying drawing, the figure of which is a simplified illustration of a preferred embodiment of the invention.

Referring to the drawing, 1 represents a large diaphragm and 2 a small diaphragm. 3 designates a light but rigid armature actuated by some form of magnetic system, such as' 4. The armature 3 is suitably connected, as indicated, to the mid ints of the two diahragms. The small iaphragm 2 is shown 111 front of the large diaphragm 1, connection between the small diaphragm and the armature being effected through a small opening in the large diaphragm. A horn 5 is provided to give eflicient coupling between the small diaphragm and the air.

It will be readily understood that the small diaphragm, due to its minute mass and relatively great stifi'ness. can be given a high natural resonance while the large diaphragm, having much greater mass and less stiffness, will have a low natural frequency. It will be noted that the driving force is applied to the common armature 3. Let us now consider what ha pens. when the armature is actuated by a ow frequency driving force. The small diaphragm due to its great stiffness and high natural period, presents a large mechanical im ance to the m ot1on of the armature w ile the large. diaphragm presents a relatively small one. The result will be that the end of the armature connected to the small diaphragm will remain practically stationary while the end connected to the large diaphragm will vibrate vigorously. On the other hand, when a high frequency driving force actuates the armature, the end attached to the large diaphragm will, in effect, form a fulcrum, due to the great mass of the diaphragm, and the small iaphragm will vibrate.

An efficlent doubly resonant loud speaker possesses many advantages which are well adjustment slight changes in the quality can be readily effected.

It will be obvious that the general principles herein disclosed may be embodied in many other organizations widely differentfrom those illustrated without departin from the spirit of the invention as defined in the following claims.

What is claimed is: v

1. In a sound reproducer, a diaphragm having a high natural period, a diaphragm having a low natural period, and means to apply a driving force to said diaphragms, said. means being so related to the diaphragms that when a low frequency driving force is applied to the system the diaphragm having a high uperiod will offer alarge mechanical imp ance to the driving force so that the driving force will be most effective upon the diaphragm of low frequency.

2. In a sound reproducer, a diaphragm having a high natural period, a. diaphragm having a low natural period, and means to apply a driving force to said diaphra said means being so related to the diaand when a high frequency driving force is applied to the system the low frequency diaphragm will offer a large im edance to the driving force so that it wil be most effective upon the high frequency dia- 3. In a sound reproducer, a small diaphragm having small mass and relativel great stiffness so that its natural period W1 1 e high, a large diaphragm having a greater mass and less stiffness so that its natural period-will be low, and means to apply a driving force to said diaphragms, said means bein" so related to the diaphragms that when a ow frequency driving force is applied to the system the diaphragm having a high period will offer a large mechanical impedance to the driving force so that the drivin force will be most effective upon the diap ragm of low frequency.

4. In a sound reproducer, a small diaphragm having small mass and relativel reat stiffness so that its natural period wi 1 be high, a large diaphragm having a greater mass and less stiffness so that its natural pe riod will be low, and means to apply a driving force to said diaphragms, said means belng so related to the diaphragms that when a low frequency driving force is applied to the system the diaphragm having a high period will offer alarge mechanical impedance to the driving force so that the driving force will be most effective upon the diaphragm of low frequency and when a high frequency driving force is applied to the system the low frequency diaphragm will offer a large impedance to the driving force so that it will be most effective upon. the high frequency diaphragm.

5. In a sound reproducer, a small diaphragm having small mass and relatively reat stiffness so that its natural period will be high, a large diaphragm having a greater mass and less stiffness so that its natural period will be low, means to produce a driving force, and a lever arrangement for applying said force to the diaphragms, said lever arrangement being so related to the diaphragms that when a low frequency driving orce is applied to the system the small diaphragm presents a large mechanical impedance and the driving force will be principally applied to the large diaphragm.

6. In a sound reproducer, a small diaphragm having small mass and relatively great stiffness so that its natural period will be high, a large diaphragm having a greater mass and less stiffness so that its natural eriod will be low, means to produce a driving force, and a lever arrangement for applying said force to the diaphragms, said ever arrangement being so related to the diaphragms that when a low frequency driving force is applied to the system the small dia hragm presents a lar e mechanical impedance and the driving Force will be principally applied to the large diaphragm, and when a high frequency driving force is applied to the system the large diaphragm will present a large mechanical impedance so that the driving force will be principally applied to the small diaphragm.

7. In a sound reproducer, a small diaphragm having small mass and relatively great stiffness so that its natural period will be high, a large diaphragm having a greater mass and less stiffness so that its natural period will be low, means to produce a driving force, a lever operated b said means, said lever being connected to t 1e two diaphragms so that it may be, in effect, fulcrumed about its point of connection with either diaphragm, and the driving force being so ap plied to the lever that when it is actuated y a low frequency driving force the small dialphragm presents a large mechanical impe ance and the lever applies the energy to the large diaphragm.

8. In a sound reproducer, a small diaphragm having small mass and 'relativel great stiffness so that its natural period wi 1 be high, a large diaphragm having a greater mass and less stiffness so that its natural period will be low, means to produce a driving force, a lever operated b said means, said lever being connected to t 0 two diaphragms so that it may be, in effect, fulerumed about its point of connection with either diaphragm, and the driving force being so applied to the lever that when it is actuated by a low frequency driving force the small diaphragm presents a lar e mechanical impedance and the lever applies the energy to the large diaphragm, while the application of, a high frequency driving force to the lever permits the large diaphragm to offer a relative] lar e mechanical impedance so that the orce is effectively applied to the small diaphragm.

9. In a sound reproducer, a small diaphragm having small mass and relatively great stiffness so that its natural period-will be high, a large diaphragm having a greater mass and less stiffness so that its natural period will be low, means to produce a driving force, a lever operated by said means, said lever being connected to the two diaphragms so that it may be, in effect, fulerumed about its point of connection with either diaphragm, the drivin force being so ap lied to the lever that w en it is actuated y a low frequency driving force the small diaphragm presents a large mechanical impedance, and the lever applies the energy to the lar e diaphragm, while the application of a hig frequency driving force to the lever permits the large diaphragm to offer a relatively large mechanical impedance to the large diaphragm, while the application of a high frequency driving force to the lever permits the largediaphragm to ofl'er a relatively large mechanical impedance so that the force is efiectively applied to the small diaphra m, and means to adjust the point at 1 WhlCh t e driving force is applied to the lever with respect to its two eflective fulcrums.

In testimony whereof, I have signed my name to this specification this 31st day of ll March 1924. j

BRUN SON S. MQGUTCHEN. 

